Watch: These are the reasons all animals don't have identical lifespans (and turtles outlive us)

An Icelandic clam is just hitting the prime of life.

Everyone knows that the tortoise can live for more than 100 years. Maybe fewer people know that the microscopic lab worm spends only a few short weeks on the planet.

Lifespan differences are vast among animals. While mice and rats live for around four years, the bowhead whale may only experience death after 200 long years.

Why these differences? What does it even mean to age? The video above has some answers.

Animals start the process of ageing after reaching sexual maturity. While the drivers can be complicated, ageing is essentially related to cell death and dysfunction. When we’re younger, it’s easier to regenerate cells and replace dying ones quickly. Getting older means our systems aren’t as efficient as they used to be, leading to disease and, eventually, death.

But why then do animals have such major variance in their lifespans? This can be traced to several factors such as their body size, the environment and more. Ming, an Icelandic clam known as an ocean quahog, leads the longevity race among vertebrates with an incredible 507 years. In more mindboggling news, the Antarctic glass sponge can make it for over 10,000 years in frigid waters.

Heart-rates and metabolic rates are known to slow down in colder environments which may lead to these creatures and organisms ageing slowly compared to the rest of us. Often, larger species do seem to live longer than the smaller ones, some of whom often fall prey to predators in the food chain. But there are notable exceptions to the size-rule: Bats, birds, moles, and turtles.

Other factors that may affect longevity include genetic differences. As for humans, our average life expectancy clocks in at 71 years currently. Nowhere close to those who manage to survive the longest on our planet, of course. In better news, we’re very good at increasing life expectancy.